docs: def print_structure(self, tostring=False):
          """
          ## FOR DEBUGGING ONLY ##
          Pretty-prints the structure of the tree.
          If tostring is true, prints nothing and returns a string.
          :rtype: None or str
          """
          if self.top_node:
              return self.top_node.print_structure(tostring=tostring)
          else:
              result = "<empty IntervalTree>"
              if not tostring:
                  print(result)
              else:
                  return result